In hot conditions and with a vocal crowd of supporters, Flies were always the favourites boosted by the experience and skill of PNG Palais players in Cathy Neap and Helen Abau, and took a 10-4 lead at half time.
The lead was pushed out to 14-4 early in the second half when Abau crossed over in the corner.
But the Royals girls hit back immediately from the restart through a barging Naomi Kaupa who proved too hard to stop close to the line.
An unsuccessful conversion left the score at 14-8 with the Royals needing a converted try in the dying minutes to level up.
But the girls from Hohola held on until the final siren to fly away as the 2017 women’s champions of the MRDC 9s.
In the Plate grand final earlier, Sisters had the easiest of wins after forfeiting Souths.
Souths finished as winners in the Bowl division.
To the men’s, in the Cup grand final, Tarangau (2) beat Royals (1) 20-16 in a thriller that was decided in golden point time.
Wests (2) won the Plate after beating Dobo Warriors 16-4, while for the Bowl, Wests (1) edged out Kone Storms (2) 12-8.